214 THE POPULAR SCIENCE MONTHLY. 



Carbonic-acid gas is the element which, in deep mines and vaults, 

 causes almost instant insensibility and suffocation to persons subjected 

 to its influences, and instantly extinguishes the flame of any light 

 lowered into it. The normal quantity of this gas contained in the air 

 we breathe is *04 ; one per cent of it causes distress in breathing ; two 

 per cent is dangerous ; four per cent extinguishes life, and four per 

 cent of it is contained in air expelled from the lungs. According to 

 Dr. Tidy's table, each ordinary jet of common gas contributes to the 

 air of a room sixteen by ten feet on the sides and nine feet high, con- 

 taining 1,440 cubic feet of air, twenty-two per cent of carbonic-acid 

 gas, which, continued for twenty hours without ventilation, would 

 reach the fatal four per cent. 



Professor Huxley gives, as a result of chemical analyses, the fol- 

 lowing table of ratio of carbonic-acid gas in the atmosphere at the 

 points named : 



On the Thames, at London - 0343 



In the streets of London - 0380 



Top of Ben Nevis -0327 



Dress circle of Haymarket Theatre (11.30 p. m.) -0757 



Chancery Court (seven feet from the ground) *1930 



From working mines (average of 339 samples) '7852 



Largest amount in a Cornish mine 2'0500 



In addition to the consumption of oxygen and production of car- 

 bonic acid by the use of common gas, the gas itself, owing to defect- 

 iveness of the burner, is projected into the air. Now, considering 

 the deleterious nature of all illuminating gases, the reasons for perfect 

 ventilation of rooms in which natural gas is used for heating and 

 culinary purposes are self-evident, not alone as a protection against 

 explosions, but for the health of the occupants of the house, remem- 

 bering that a larger supply of oxygen is said to be necessary for the 

 perfect combustion of natural than of common gas. 



Carbonic oxide, formed by the consumption of carbon, with an in- 

 sufficient supply of air, is the fatal poison of the charcoal-furnace, not 

 infrequently resorted to, in close rooms, as a means of suicide. The 

 less sufficient the air toward perfect combustion, the smaller the quan- 

 tity of carbonic acid and the greater the amount of carbonic oxide. 

 That is to say, at the time of ignition the chief product of combus- 

 tion is carbonic oxide, and, unless sufficient air be added to convert the 

 oxide to carbonic acid, a decidedly dangerous product is given off into 

 the room. Yet, by means of a flue to carry off the poisonous gases 

 from burning jets, the combustion of gas, creating a current, is made 

 an aid to ventilation. Unfortunately, this important fact, if commonly 

 known, is not much heeded by heads of families or builders of houses. 

 But in any large community where gas comes into general use as an 

 article of fuel, this fact will gradually become recognized and re- 

 spected. 



